Re-landing "UMA metrics for fractions of wheel and touch scrolls blocked on the main thread."

ui/events/blink/input_handler_proxy.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_
 #define UI_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_
 
 #include <memory>
 
 #include "base/containers/hash_tables.h"
@@ skipping 100 matching lines @@
   bool scrollBy(const blink::WebFloatSize& offset,
                 const blink::WebFloatSize& velocity) override;
 
   bool gesture_scroll_on_impl_thread_for_testing() const {
     return gesture_scroll_on_impl_thread_;
   }
 
  protected:
   void RecordMainThreadScrollingReasons(blink::WebGestureDevice device,
                                         uint32_t reasons);
+  void RecordScrollingThreadStatus(blink::WebGestureDevice device,
+                                   uint32_t reasons);
 
  private:
   friend class test::InputHandlerProxyTest;
   friend class test::InputHandlerProxyEventQueueTest;
 
   void DispatchSingleInputEvent(std::unique_ptr<EventWithCallback>,
                                 const base::TimeTicks);
   void DispatchQueuedInputEvents();
 
   // Helper functions for handling more complicated input events.
@@ skipping 107 matching lines @@
 
   bool smooth_scroll_enabled_;
   bool uma_latency_reporting_enabled_;
   bool touchpad_and_wheel_scroll_latching_enabled_;
 
   // The merged result of the last touch start with previous touch starts.
   // This value will get returned for subsequent TouchMove events to allow
   // passive events not to block scrolling.
   int32_t touch_start_result_;
 
+  // The result of the last mouse wheel event. This value is used to determine
+  // whether the next wheel scroll is blocked on the Main thread or not.
+  int32_t mouse_wheel_result_;
+
   base::TimeTicks last_fling_animate_time_;
 
   // Used to record overscroll notifications while an event is being
   // dispatched.  If the event causes overscroll, the overscroll metadata can be
   // bundled in the event ack, saving an IPC.  Note that we must continue
   // supporting overscroll IPC notifications due to fling animation updates.
   std::unique_ptr<DidOverscrollParams> current_overscroll_params_;
 
   std::unique_ptr<CompositorThreadEventQueue> compositor_event_queue_;
   bool has_ongoing_compositor_scroll_pinch_;
 
   std::unique_ptr<base::TickClock> tick_clock_;
 
   DISALLOW_COPY_AND_ASSIGN(InputHandlerProxy);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_BLINK_INPUT_HANDLER_PROXY_H_